Here, we're first importing a new aspect from Kivy, Line. This is so we can draw a line.

Now, we modify our on_touch_down to, using the canvas, which is part of our inherited Widget, we're going to start defining our line as a Line element, where the points are just one point for now, which is the x,y coordinates of our touch_down.

Next, we modify our on_touch_move method to modify our touch.ud["line"] by appending the new touch.x and touch.y coordinates, so now we have more coordinates, drawing a line using them.

Finally, we modify the SimpleKivy4 root app to return our new DrawInput class, which will now give us an app that allows us to draw!